1. Field of the Invention
The present invention relates to a method of slicing a semiconductor wafer and an apparatus therefor, in particular, to a method of slicing a semiconductor wafer and an apparatus therefor in which a bowl-shaped wafer can be manufactured.
2. Description of the Related Art
A blade tip portion of an inner peripheral cutting edge or an outer peripheral cutting edge is composed of fine diamond grains. The blade tip is abraded partially by use. A cutting curve in either direction is drawn according to this partial abrasion. For instance, when a cutting blade is curved upward by the abrasion, a shape of a wafer is curved more upward according to a increase in a cutting resistance as cutting progresses, so that the curving displacement of the upper side becomes the maximum because the cutting resistance is made maximum at the maximum cutting length. When the cutting is further progressed, the cutting resistance becomes small according as a cutting length gradually becomes small, so that the curving displacement becomes also small gradually.
The above-mentioned method of slicing has a problem in that a wafer is worked in a shape curved upward or downward. Conventionally, a curving control of the wafer is executed to eliminate the problem. That is, the blade displacement is detected with a sensor, and the curving control is performed in such a manner that the blade displacement at the position of this sensor becomes zero by moving the air pad. In another conventional curving control, an air pad is moved in a manner that the displacement of the center part at the cutting position of a semiconductor material becomes zero, and the semiconductor material is cut.
However, the conventional method of slicing has a disadvantage in that a wafer is formed like a part of cylinder or a saddle as shown in FIGS. 4 (A) and (B) because the air pad is controlled in such a manner that the blade displacement of a sensor position or a center position becomes zero.
The wafer forming a part of cylinder and the saddle-shaped wafer are disadvantageous for the postprocessing of the wafer unlike a bowl-shaped wafer shown in FIG. 5.